The present invention relates to a package for decayable foodstuffs, which package consists of a package material and forms a mainly closed package space and a mainly closed indicator space for an oxidation indicator.
Specification EP 0627,363 presents a foodstuff package containing an indicator that changes its colour when the concentration of gas inside the package reaches a predetermined level. The indicator may consist of a label or printed material formed on the surface of the package. The indicator may be separated by a gas-permeable foil from the product contained in the package. The indicator may be a carbon dioxide or oxygen indicator. However, such an indicator only responds to gas penetrating into the package or gas formed inside the package. The indicator does not respond to ageing of the packge and/or to a rise in the temperature of the package.
Specification EP 0629497 presents a package material that comprises two foils joined together and forming between them a space for a colour indicator. When the package material is damaged, the colour indicator reacts with the gas entering into the package and changes its colour. However, such a leakage indicator only responds when the package material is damaged, it does not respond to decay of the foodstuff in itself.
Specifications U.S. Pat. No. 4,772,707, JP 55-41875, JP 61-152299, JP 62-259059 and FI 94802 present various absorbents for absorbing the oxygen remaining in the package, stabilisers, such as reducing agents, for stabilising a colorant before the foodstuff is packaged, and colorants for indication of gas penetrating into the package e.g. via a leakage or decay of the foodstuff. The indicators proposed in these specifications are placed in the package in conjunction with the packaging of the foodstuff; in other words, the indicators are separate from the package and they are manufactured separately. The manufacture and especially the storage of this kind of separate indicators before they are placed in a package is difficult as the indicators tend to react with oxygen as soon as they come into contact with ambient air. Further difficulties arise from the separate manufacture, storage and handling of the indicators.
Generally, the specifications referred to above relate to various leakage indicators designed for use in foodstuff packages and indicators that respond to damage of the package and decay in itself. However, the specifications referred to do not describe an indicator or package that would respond to ageing of the package and/or to an excessive rise in the temperature of the package and to the volatile compounds produced as a result of decay of the foodstuff.